It is necessary, in many instances, to monitor the fluid depth in containers or in storage or holding pools. Where the stored fluid is potentially toxic, the requirement for fluid depth monitoring is of enhanced importance.
Along with appropriate sensors and readout systems, the persons responsible for the fluid storage need to feel confident that the depth or fluid level gauge is accurate at all times. Some kind of operability verification apparatus and procedure is required. In the past, removing the gauge to a remote location for calibration and function testing was the recognized way to verify the operability and accuracy of the system.